Actually... Thinking about it. What is vinegar? It's an acid right? You're using laundry detergent (which I believe is basic). So wouldn't you be negating what you're doing with the detergent/vinegar thing?

Wouldn't it be better to just wash without vinegar or detergent in that case? You would get some sort of salt forming from the vinegar/detergent thing. I'm not sure if it's a soluble salt or insoluble but you'd still be pretty much dumping a slightly basic salt on your clothes doing that.

That's just from a scientific point of view. I think I'm going to try this trick a few times and see if there's actually a difference.